The present invention relates to a cyclone furnace. More specifically, it relates to a cyclone furnace that has a powder-supply pipe to feed a powder for combustion and/or melting, such as dry sludge particles, coal particles or exhaust ash, in such a fashion that the powder-supply pipe feeds the powder across a vortex or cyclone of burning gas generated by carrier gas.
Conventionally, such furnace for combusting and/or melting powders of, for example, dry sludge particles, as shown in FIG. 3, has a cylindrical furnace body 20 of a circular cross section, air-supply pipes 31A through 31D for generating an intense velocity disposed tangentially to the body 20, and powder-supply pipes 32A through 32D disposed through the air-supply pipes 31A through 31D, respectively. The powder-supply pipes 32A through 32D open in the air-supply pipes 31A through 31D, respectively, thereby conveying the powder tangentially to the vortex.
The powder is then accelerated by the air from the air-supply pipes 31A through 31D, and is carried directly thereby with little diffusion, impacts on small sections of the internal peripheral surface of the body 20. The small sections are defined by an angle .alpha. at approximately 17.degree. viewed from the center axis of the furnace 20, that is, the center axis of the vortex. The powder impacts the narrow sections at a relatively large impact angle in a range of from 20.degree. to 42.degree.. Consequently, the small sections are eroded after a time. The rate of erosion is increased by the high temperature atmosphere in the body 20, thereby rapidly eroding the wall of the body 20 at a few points.